Magnetic measurements using inductance measurements

Abstract

The keys are fitted with small magnets and the movement of each key is detected and measured with inductive sensors that are adjacent to a ferrite member. The properties of the ferrite member change due to the proximity of the magnet, and these changes influence the inductive measurements. The ferrite member can be used to seal the electronics in a keyboard making it less prone to malfunction when coffee or other fluids are spilled onto it.

1 . A switch mechanism for determining multiple points of depression as a switch is actuated, said switch comprising a magnet that moves in response to depression of a key and an inductor/ferrite combination the inductance of which is measured, wherein said measured inductance reflects the distance between the said magnet and the said inductor/ferrite combination. 
     
     
         2 . A method of implementing a non-ohmic contact switch by measuring the inductance of an inductor with a ferrite member adjacent to said inductor, said ferrite member being affected by a magnet being moved relative to the ferrite member under user actuation in such a way that the inductance measured in the inductor changes, and wherein said switch is configured to provide information about multiple points of said movement during user actuation. 
     
     
         3 . A method of implementing a magnetic rotation sensor using multiple inductor and ferrite combination units placed near a magnet that is mounted on an axle to enable rotation, and wherein the measured changes in inductance of the inductors reflect the rotation of the magnet. 
     
     
         4 . The method according to  claim 2  which includes the steps of using multiple switches in a keyboard wherein each switch is implemented as per  claim 2  and of positioning a sealing layer between moving parts of the keyboard and the inductors of the switches. 
     
     
         5 . The switch mechanism of  claim 1  wherein said combination comprises a ferrite member adjacent a coil of an inductor which is located on a pcb and said pcb is sealed by means of a sealing layer or by said ferrite member which is provided as a sheet of ferrite. 
     
     
         6 . The switch mechanism of  claim 1  which includes an LED and wherein the ferrite in said combination comprises a ferrite layer through which the LED protrudes. 
     
     
         7 . A switch mechanism which comprises a pcb, an inductor on the pcb, a ferrite member which overlies a coil of the inductor, a spring, a magnet which is movable by a user against action of the spring towards the coil and wherein the ferrite member and inductor are configured such that flux from the magnet affects properties of the ferrite which produce a change in the measured inductance of the inductor.